That can happen with any Mare of any age- a difficult birth. These horses are obviously well cared for and well loved, and have any help they need from their Vet.... They lead a better life than many. What do you imagine happens in the wild? Many mares and foals die giving birth in the wild. I know my sis only has her mares bred a few times, but she does it for quality hunter & dressage horses. Not as a business of selling horses. Mares are always exhausted after birth, some more difficult than others. Did you watch a few of the summertime videos, like the one calling the horses in? The mares all come running, with their colts/fillies beside them. To me, it looks like they have a very wonderful life.
Here is a little info...:
Horses are mammals, and like all mammals give birth to live offspring who are nourished for the first part of their life by their mother's milk. A mare can only produce one foal per year. A stallion is capable of producing around two hundred foals per year. A mare is capable of producing a foal at about eighteen months of age, but it is healthier for mare and foal if the mare is at least four years old. A stallion can start breeding mares as early as two years (in some cases earlier), but it is healthier for the young stallion if breeding does not begin until four years. In both cases, early breeding may affect growth.
A mare may continue carrying foals until they are in their late twenties. A stallion may continue breeding mares into his twenties, although his potency will decline.
Foals are able to walk and run a few hours after birth. They may nibble grass, concentrate or hay within a few days after birth, although their mother’s milk will be the main source of nutrition. They may be weaned from their mothers as early as three months after birth, although many breeders choose to leave mares and foals together longer.
Although feral horses mate and give birth without the attention of a veterinarian, many problems can be circumvented by having the stallion checked before breeding, and mare checked and cared for properly during the gestation period.